The present invention relates to computer networks and in particular to a method of configuring a network to allow access to network devices.
In recent times, mobile telephones have become more sophisticated and now often contain a wireless networking controller in addition to the usual radio transceiver capable of accessing cellular data packet networks using a protocol such as the General Packet Radio Service (GPRS), High Speed Packet Access (HSPA) or Long Term Evolution (LTE). The wireless networking controller may operate under at least one of the IEEE 802.11 family of Wi-Fi™ standards such as 802.11a, 802.11b, 802.11g or 802.11n to generate a wireless network which will hereinafter be referred to as a wireless local area network (WLAN).
Cellular data packet networks provide network access via a mobile phone operator's data network and therefore provide broad geographical network access.
In WLAN setups, a router device typically provides a wired connection to a wide area network such as the Internet and a wireless controller for providing a wireless access point. This enables network access for local mobile devices in the nearby vicinity. Within the wireless network provided by the wireless router, the wireless router functions as a gateway for the connected devices to communicate with other devices located remotely on the Internet. In this way the devices “share” an Internet connection. It is also possible for these devices to communicate with each other on the local network, for example to directly access shared resources on individual device, to access a Network Access Storage (NAS) device or a networked printer. The wireless router provides security by using a firewall to prevent access to the internal network.
With dual access to a data network, the user can choose which connection to use in dependence on their current situation and location. For example, while travelling, a 3G connection allows the user to maintain a connection over a wide geographical area. In contrast, at home, a WLAN connection would provide a faster connection but within a limited range.
Currently the user must explicitly choose which connection they wish to use, or alternatively they can set a default connection in which case they must explicitly set a different connection when desired. When the connection type changes, then any existing sessions will be lost which may interrupt any services currently running on the mobile device. For example, if the user is listening to a music streaming application, if they are in the vicinity of a WLAN spot and wish to use a WLAN connection, then the music stream will be interrupted since the mobile device's IP address will have changed.
Mobile IPv6 and Proxy Mobile IPv6 (PMIP) are networking protocols developed to address the issue of mobile node mobility. In both schemes, the mobile device is assigned an IP address which is maintained by the mobile node as it moves from one connection to another. This ability is provided by a Local Mobility Anchor (LMA) and a plurality of Mobile Access Gateways (MAGs). For each mobile device, the LMA provides a “home” address which is seen by external correspondent devices located on the Internet. All communication between the mobile device and the correspondent devices is channelled via the LMA and a tunnel is created between the LMA and the MAG closest to the mobile device. When the mobile device moves to a different location, the LMA is informed of the change and if necessary a handover procedure is carried out to destroy the existing tunnel with the previous MAG and to create a new tunnel to the new serving MAG.
In this way, session continuity is enabled by providing a session anchor point at the LMA which gives an external impression that the mobile node has a single, unchanging home IP address regardless of which access network is being used at any given time.
However, the requirement for directing all traffic through a tunnel between the LMA and the MAG to enable a consistent home IP address can be restrictive. Particularly in a case where the mobile device is attached to a WLAN wireless router in a local wireless network, the mobile device is not able to connect directly to other devices in the local area network.
For example, if a user of a mobile device such as a smart phone operating under a session continuity solution such as PMIP, is listening to internet radio on the way home using a 3G connection. When the user arrives home, the smart phone detects the user's WLAN access point and therefore gives the user the option to connect to the WLAN. The user has two choices:                1) connect using a session continuity solution such as PMIP, establish a tunnel to the LMA and maintain their internet radio session, but lose access to their home media server; or        2) connect directly to their home LAN and have the internet radio session break as their IP address changes.        
It is desirable to enable the user to maintain session continuity when they leave or enter their own home, and to enable them to communicate with the other devices on their home LAN. In particular, it is desirable that the user's mobile device can communicate directly (via only the local wireless access point) with other devices on the home LAN when they are actually at home. It also enables them to communicate with the same LAN devices via their home broadband link when they are not at home.
In one aspect the present invention provides a method of accessing resources on a data network, the data network having a mobile node, access routers and secondary routers arranged such that the mobile node can connect to different ones of the access routers while maintaining a consistent network address to other devices, the mobile node having an associated home sub-network maintained by a home access router, the method comprising: identifying the network address of the home access router corresponding to the mobile node; modifying a routing table of the home access router to allow data packets to be exchanged between the mobile node and resources located on the home sub-network.
In another aspect, the present invention a data network comprising: a mobile node; a plurality of access routers and secondary routers arranged such that the mobile node can connect to different ones of the access routers while maintaining a consistent network address to other devices, the mobile node having an associated home sub-network maintained by a home access router; means for identifying a network address of a home access router associated with a home sub-network of the mobile node; and means for modifying a routing table of the home access router to allow data packets to be exchanged between the mobile node and resources located on the home sub-network.